Tag Archives: overwintering

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Extremely cold temperatures were experienced throughout Manitoba at the end of December and beginning of January. The cold temperatures combined with limited amounts of snow cover have many winter wheat producers thinking about winter survival.

Manitoba Agriculture’s Ag Weather Program has been monitoring soil temperatures in winter wheat fields for a number of years. There are currently three weather stations measuring real time soil temperatures in winter wheat fields at Alexander, Dauphin, and Kleefeld. The data collected from the weather stations is made available to the University of Saskatchewan and Western Ag Labs for their Winter Cereal Survival Model, available at: https://www.wheatworkers.ca/wcsm.php. The Winter Cereal Survival Model compares the cold tolerance of winter wheat varieties to the daily average soil temperature at crown depth (about 1”).

Plotting the soil temperatures against hardiness curves can give an early indication if there is a concern for winter injury or winterkill. Factors that can impact the level of cold hardiness of the plant include weather, fertility, seeding date, and seeding depth. In Manitoba, the majority of winter wheat acres would likely be considered to be well-hardened. The figure below shows soil temperatures at 1” depth in three winter wheat fields in Manitoba, plotted against three hardiness curves.

Soil temperatures in Alexander and Dauphin dipped below the low hardiness curve, but have not approached the mid and high-hardiness curves at this point. To assess the level of risk on your farm consider how well-hardened your field may be and check your fields for level of snow accumulation. It is still early in the season, so check back in on the Winter Wheat Survival Model throughout the winter to get an idea of the risk of winterkill in your area.

The vast majority of corn in Manitoba is in the bin, but what about those few fields that may not be harvested yet? In some cases weather conditions may have made it difficult for farmers to harvest corn in the fall, but some farmers may decide that the corn moisture level and costs associated with drying mean that it is more economical to leave corn in the field to let it dry down naturally over winter.

Just how much dry down can be expected over winter? The amount of drying that occurs in the field depends on the corn maturity, variety, and moisture content, as well as environmental factors such as temperature, humidity, solar radiation, and wind speed. Field drying is extremely slow in the winter, and corn will only dry to about 20 to 21% moisture content. In a typical year, it is expected that corn will dry approximately 11-12% in October, 4-5% in November, and just 2% per month in December and January (Table 1).

Table 1. Estimated corn field drying

Month

EMC (%)*

GDD

PET (in.)

Estimated Drying (% pt.)

Month

Week

Sept

15

250-350

4-5

18

4.5

Oct

16

100-125

2.8-3.5

11-12

2.5

Nov

19

20-30

0.8-1.2

4-5

1

Dec

20

0

0.5-0.8

2

0.5

Jan

21

0

0.5-0.8

2

0.5

Feb

21

0

0.5-0.9

3

0.8

Mar

19

0

1.3-1.6

5

1

Apr

16

50-90

3.2-4.5

16

4

May

14

200-300

6.5-8.5

30

7

*EMC – equilibrium moisture content, GDD – growing degree days, PET – potential evapotranspiration 1EMC is the moisture content to which corn will dry and is based on air temperature and relative humidity

Risks of overwintering corn Heavy snowfall during the winter can cause significant amounts of lodging resulting in yield losses. Root and stalk strength should be taken into consideration when deciding if a field should be overwintered. Research conducted at the University of Wisconsin examined corn yield loss during the winter (Table 2).

This researched showed that in 2000, a year with heavy snow cover, yield loss was much greater than in 2001, a year with very little snow cover. Standing corn may result in more snow catch and slow soil drying in the spring, which could delay planting.

Table 2. Percent yield loss of corn left standing in the field through winter at Arlington, Wisconsin.

Corn can be harvested throughout the winter if conditions are cool and there isn’t much snow. If stalks stay standing throughout the winter, and ear drop and wildlife damage are limited, corn can get through the winter without much yield loss. Yield loss throughout the winter will vary by hybrid and environmental conditions.

If you are planning to over winter corn please contact your local MASC agent.

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Reference material

Diseases: New clubroot cases have been confirmed in the Rural Municipalities of Lorne and Dufferin. Insects: Scouting for bertha armyworm continues with some reports of insecticide applications. Spider mites being noticed in some soybean fields. Grasshopper populations are variable. For full report see Insect & Disease Report – August 1, 2018

Crops are advancing rapidly with the warm and dry conditions. Rain is needed in most areas to sustain crops and replenish soil moisture. Harvested has started in winter cereals, barley, and peas. Swathing or pre-harvest applications have started in early seeded spring cereals and canola. Fist cut hay is nearing completion; yields are below normal. […]

Diseases: The second case of clubroot in canola this year has been reported. Disease surveys in soybean and wheat are ongoing and disease levels are low overall. Insects: Overall insect concerns in field crops are relatively low. There are still some areas where grasshopper levels are being watched. Spider mite levels are being monitored in some soybean fields in […]

Disease – Goss’s wilt was observed near St. Claude. Insects – Grasshopper populations are being monitored in and around the edges of some fields. Armyworms have been noticed in some cereal fields in the Central and Eastern regions. No soybean aphids have been reported yet. For more details and information see http://www.gov.mb.ca/agriculture/crops/seasonal-reports/manitoba-insect-and-disease-update-2018-07-11.html

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Favourable weather and field conditions have allowed seeding operations to begin, with a provincial estimate of <5% of the 2017 crop seeded. For the full crop report, see on-line at http://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/crop-report-2017-05-01.html

The Guide to Crop Protection provides information on the use of herbicides, fungicides and insecticides for control of weeds, plant diseases and insects. This publication is only a guide. Always refer to the product label for application details and precautions. It is available: online at https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp. Individual sections on Weed Control, Plant Disease Control and Insect […]

Did you know you can view the 2017 edition of Seed Manitoba, as well as past editions, on www.seedmb.ca? Well, you can! Flip-view digital editions of the current guide (2017), as well as the six most recent editions, are available at http://www.seedmb.ca/digital-edition/. Also, full PDF versions are available at http://www.seedmb.ca/digital-edition/pdf-editions-and-separate-section-pdfs/ where you can download the entire […]

http://www.gov.mb.ca/agriculture/crops/plant-diseases/clubroot-distribution-in-manitoba.html Map shows positive clubroot findings by Rural Municipality, discovered through laboratory testing for presence of clubroot spores in soil and/or positive confirmation of clubroot symptomatic plants. Testing was done from 2009-2014 and is still considered limited. Positive findings have been at low spore concentrations and sporadic throughout the province. As more fields are sampled, the map will be updated. As less than […]